This research represents an investigation of the mechanisms of action of the cancer chemotherapeutic platinum coordination complexes, as well as investigation of the mechanisms of cellular resistance. Three cell lines will be used: a) a murine leukemia L1210 cell line that is sensitive to the action of both cis-diaminedichloroplatinum(II) (cis-DDP) and diaminocyclohexaneplatinum analogues (DACH-Pt), b) an L1210 cell line specifically resistant to cis-DDP (L1210/DDP), c) an L1210 cell line specifically resistant to DACH-Pt (L1210/DACH). The intention is to compare these three cell lines with respect to the uptake and DNA binding of the drugs and the subsequent ability of DNA repair processes to effect removal of the lesions. The interaction of cis-DDP with DNA has now been fully characterized. These studies were made possible by synthesis of a radiolabeled analogue of cis-DDP, namely [3H]-cis-dichloro(ethylenediamine)platinum(II) (cis-DEP) a drug to which L1210/DDP is similarly resistant. DNA repair inhibitors will be used to elucidate the involvement of specific DNA repair pathways in L1210 cells that have been incubated with [3H]-cis-DEP. An attempt will be made to purify the repair enzymes and assess any difference between the sensitive and resistant cells. Studies on DACH-Pt will be initiated by characterizing its interaction with nucleosides and purified DNA using enzyme digestions and high pressure liquid chromatography separation of the adducts. To facilitate these studies it is proposed to synthesize [3H]-DACH-Pt. This drug can then be used to investigate DNA repair processes that might be different in L1210/DACH cells. A further aspect will be to analyze specific proteins that are crosslinked to DNA by the platinum analogues and to compare their rates of repair.